Is 'data' a reserved property name on ctools export objects?

the field_group module uses the 'data' keyword in its exportable definitions. For example:

/**
 * Implements hook_field_group_info().
 */
function cw_event_field_group_info() {
  $export = array();

  $field_group = new stdClass();
  $field_group->disabled = FALSE; /* Edit this to true to make a default field_group disabled initially */
  $field_group->api_version = 1;
  $field_group->identifier = 'group_tab_media|node|cw_event|form';
  $field_group->group_name = 'group_tab_media';
  $field_group->entity_type = 'node';
  $field_group->bundle = 'cw_event';
  $field_group->mode = 'form';
  $field_group->parent_name = 'group_tabs';
  $field_group->data = array(
    'label' => 'Media',
    'weight' => '18',
    'children' => array(
      0 => 'field_cw_media_main_image',
      1 => 'field_cw_media_media',
    ),
    'format_type' => 'htab',
    'format_settings' => array(
      'formatter' => 'closed',
      'instance_settings' => array(
        'description' => '',
        'classes' => '',
        'required_fields' => 1,
      ),
    ),
  );
  $export['group_tab_media|node|cw_event|form'] = $field_group;

  return $export;

In some cases, when the feature is regenerated, the content of the data array gets completely wiped out, resulting in a broken field_group default object. I spent a long time tracing this, and managed to trace it to the ctools_export_load_object() function. The behaviour seems to change depending on where it's called from. If you call it standalone, then the data property is properly included, but sometimes, when called from within Features export, it isn't. Possibly something to do with caching. ->data itself gets lost, but the individual array keys within that array are flattened out the outer array.

If I rework field_group to store this data somewhere other than ->data, then everything exports ok. The _ctools_export_get_defaults_from_cache function does look like it it makes some special use of the 'data' keyword, but I don't see anything in the documentation that indicates that 'data' is a reserved keyword and should not be used. Is it reserved? Is this possibly just some undocumented behavior?